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Abstract:

A semiconductor device connected to the display panel including the
in-cell type touch sensor is configured as follows. The semiconductor
device includes a driving circuit of the display panel, a touch sensing
circuit of the touch sensor, a power supply circuit that supplies a power
source to these circuits, and a bias control circuit that controls a bias
current flowing through these circuits. The semiconductor device is able
to perform a time-division operation in which one frame period of display
is divided into a plurality of display driving periods and sensing
periods. In the display driving periods, the supply of power to the touch
sensing circuit is suppressed, and/or a bias current is reduced. In the
sensing periods, the supply of power to the driving circuit is
suppressed, and/or a bias current is reduced.

Claims:

1. A semiconductor device capable of being connected to a display panel
including a touch sensor, comprising: a driving circuit capable of
driving the display panel; a touch sensing circuit which is connected to
the touch sensor; a power supply circuit that supplies a power source to
the driving circuit and the touch sensing circuit; and a bias control
circuit that controls a first bias current flowing through the driving
circuit and a second bias current flowing through the touch sensing
circuit, wherein the semiconductor device is able to perform a
time-division operation including a display driving period in which the
display panel is driven and a touch state is not detected and a sensing
period in which a touch state is detected and a driving state of the
display panel is not changed, one or more display driving period and one
or more sensing periods are included in one frame period of an image
which is displayed by the display panel, in the display driving period,
the power supply circuit reduces power supply capability to the touch
sensing circuit further than that in the sensing period, and/or the bias
control circuit reduces the second bias current further than that in the
sensing period, and in the sensing period, the power supply circuit
reduces power supply capability to the driving circuit further than that
in the display driving period, and/or the bias control circuit reduces
the first bias current further than that in the display driving period.

2. The semiconductor device according to claim 1, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, a first
regulator that outputs a first stabilized power source, supplied to the
driving circuit, from the internal power source, a second regulator that
outputs a second stabilized power source, supplied to the touch sensing
circuit, from the internal power source, the DCDC converter is able to
improve power supply capability by increasing a frequency of a boost
clock, and to reduce power supply capability by decreasing the frequency
thereof, the first regulator is able to improve power supply capability
by increasing a third bias current controlled by the bias control
circuit, and to reduce power supply capability by decreasing the third
bias current, the second regulator is able to improve power supply
capability by increasing a fourth bias current controlled by the bias
control circuit, and to reduce power supply capability by decreasing the
fourth bias current, in the display driving period, the power supply
circuit decreases the frequency of the DCDC converter further than that
in the display driving period, and the bias control circuit reduces the
fourth bias current and the second bias current further than those in the
sensing period, and in the sensing period, the power supply circuit is
able to perform control for decreasing the frequency of the DCDC
converter further than that in the display driving period, and the bias
control circuit is able to perform control for reducing the third bias
current and the first bias current further than those in the display
driving period.

3. The semiconductor device according to claim 1, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, a first
regulator that outputs a first stabilized power source, supplied to the
driving circuit, from the internal power source, a second regulator that
outputs a second stabilized power source, supplied to the touch sensing
circuit, from the internal power source, the DCDC converter is able to
improve power supply capability by increasing a duty of a boost clock,
and to reduce power supply capability by decreasing the duty thereof, the
first regulator is able to improve power supply capability by increasing
a third bias current controlled by the bias control circuit, and to
reduce power supply capability by decreasing the third bias current, the
second regulator is able to improve power supply capability by increasing
a fourth bias current controlled by the bias control circuit, and to
reduce power supply capability by decreasing the fourth bias current, in
the display driving period, the power supply circuit is able to perform
control for decreasing the duty of the DCDC converter further than that
in the display driving period, and the bias control circuit is able to
perform control for reducing the fourth bias current and the second bias
current further than those in the sensing period, and in the sensing
period, the power supply circuit is able to perform control for
decreasing the duty of the DCDC converter further than that in the
display driving period, and the bias control circuit is able to perform
control for reducing the third bias current and the first bias current
further than those in the display driving period.

4. The semiconductor device according to claim 1, wherein the power
supply circuit includes a first DCDC converter that generates a first
internal power source from a power source which is supplied from an
outside, a second DCDC converter that generates a second internal power
source from the first internal power source, and a third DCDC converter
that generates a third internal power source from the first internal
power source, and includes a first regulator that outputs a second
stabilized power source, supplied to the driving circuit and the touch
sensing circuit, from the second internal power source, and a second
regulator that outputs a third stabilized power source, which is supplied
to the driving circuit and is not supplied to the touch sensing circuit,
from the third internal power source, each of the first, second and third
DCDC converters is able to improve power supply capability by increasing
a frequency and/or duty of a boost clock, and to reduce power supply
capability by decreasing the frequency and/or duty thereof, the first
regulator is able to improve power supply capability by increasing a
third bias current controlled by the bias control circuit, and to reduce
power supply capability by decreasing the third bias current, the second
regulator is able to improve power supply capability by increasing a
fourth bias current controlled by the bias control circuit, to reduce
power supply capability by decreasing the fourth bias current, or to cut
off a supply of power, in the sensing period, the power supply circuit
reduces power supply capability by decreasing a frequency and/or duty of
a boost clock of the first DCDC converter and the second DCDC converter
and stops an operation of the third DCDC converter, and the bias control
circuit stops a supply of power from the second regulator to the driving
circuit by decreasing the fourth bias current.

5. The semiconductor device according to claim 1, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the sensing
period is set to an arbitrary period between the display driving period
and a next display driving period.

6. The semiconductor device according to claim 2, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the sensing
period is set to an arbitrary period between the display driving period
and a next display driving period.

7. The semiconductor device according to claim 3, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the sensing
period is set to an arbitrary period between the display driving period
and a next display driving period.

8. The semiconductor device according to claim 4, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the sensing
period is set to an arbitrary period between the display driving period
and a next display driving period.

9. A semiconductor device capable of connecting to a display panel,
comprising: a driving circuit capable of driving the display panel; a
power supply circuit that supplies a power source to the driving circuit;
and a bias control circuit that controls a bias current flowing through
the driving circuit, wherein the semiconductor device is able to perform
a time-division operation including a display driving period in which the
display panel is driven and a waiting period in which a driving state is
not changed, one or more display driving period and one or more waiting
period are included in one frame period of an image which is displayed by
the display panel, and in the waiting period, the power supply circuit is
able to perform control for reducing power supply capability further than
that in the display driving period, and/or the bias control circuit is
able to perform control for reducing the bias current further than that
in the display driving period.

10. The semiconductor device according to claim 9, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, and a
regulator that outputs a stabilized power source from the internal power
source, the DCDC converter is able to improve power supply capability by
increasing a frequency of a boost clock, and to reduce power supply
capability by decreasing the frequency thereof, the bias current is set
to a first bias current, the regulator is able to improve power supply
capability by increasing a second bias current controlled by the bias
control circuit, and to reduce power supply capability by decreasing the
second bias current, and in the waiting period, the power supply circuit
is able to perform control for decreasing the frequency of the DCDC
converter further than that in the display driving period, and the bias
control circuit is able to perform control for reducing the second bias
current and the first bias current further than those in the display
driving period.

11. The semiconductor device according to claim 9, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, and a
regulator that outputs a stabilized power source from the internal power
source, the DCDC converter is able to improve power supply capability by
increasing a duty of a boost clock, and to reduce power supply capability
by decreasing the duty thereof, the bias current is set to a first bias
current, the regulator is able to improve power supply capability by
increasing a second bias current controlled by the bias control circuit,
and to reduce power supply capability by decreasing the second bias
current, and in the waiting period, the power supply circuit is able to
perform control for decreasing the duty of the DCDC converter further
than that in the display driving period, and the bias control circuit is
able to perform control for reducing the second bias current and the
first bias current further than those in the display driving period.

12. The semiconductor device according to claim 9, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, and a
regulator that outputs a stabilized power source from the internal power
source, the DCDC converter is able to improve power supply capability by
increasing a frequency or a duty of a boost clock, and to reduce power
supply capability by decreasing the frequency or the duty thereof, the
bias current is set to a first bias current, the regulator is able to
improve power supply capability by increasing a second bias current
controlled by the bias control circuit, and to reduce power supply
capability by decreasing the second bias current, and in the waiting
period, the power supply circuit is able to perform control for fixing a
signal level of the boost clock of the DCDC converter, and the bias
control circuit is able to perform control for reducing the second bias
current and the first bias current further than those in the display
driving period.

13. The semiconductor device according to claim 9, wherein the power
supply circuit includes a first DCDC converter that generates a first
internal power source from a power source which is supplied from an
outside, a second DCDC converter that generates a second internal power
source from the first internal power source, and a regulator that outputs
a stabilized power source from the second internal power source, each of
the first and second DCDC converters is able to improve power supply
capability by increasing a frequency or a duty of a boost clock, and to
reduce power supply capability by decreasing the frequency or the duty
thereof, the bias current is set to a first bias current, the regulator
is able to improve power supply capability by increasing a second bias
current controlled by the bias control circuit, and to reduce power
supply capability by decreasing the second bias current, and in the
waiting period, the power supply circuit is able to perform control for
decreasing the frequency of the first DCDC converter further than that in
the display driving period, and/or decreasing the duty further than that
in the display driving period, and fixing a signal level of the boost
clock of the second DCDC converter, and the bias control circuit is able
to perform control for reducing the second bias current and the first
bias current further than those in the display driving period.

14. The semiconductor device according to claim 6, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the waiting
period is set to an arbitrary period between the display driving period
and a next display driving period.

15. The semiconductor device according to claim 7, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the waiting
period is set to an arbitrary period between the display driving period
and a next display driving period.

16. The semiconductor device according to claim 8, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the waiting
period is set to an arbitrary period between the display driving period
and a next display driving period.

17. The semiconductor device according to claim 9, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the waiting
period is set to an arbitrary period between the display driving period
and a next display driving period.

18. The semiconductor device according to claim 10, wherein the display
panel is able to display an image frame constituted by a plurality of
lines, the display driving period is a period in which some of a
plurality of lines within the image frame are displayed, and the waiting
period is set to an arbitrary period between the display driving period
and a next display driving period.

19. A semiconductor device capable of connecting a display panel
including a touch sensor, comprising: a touch sensing circuit which is
connected to the touch sensor; a power supply circuit that supplies a
power source to the touch sensing circuit; and a bias control circuit
that controls a bias current flowing through the touch sensing circuit,
wherein the semiconductor device is able to perform a time-division
operation including a sensing period in which a touch state is detected
and a waiting period in which the touch state is not detected, one or
more sensing periods and one or more waiting period are included in one
frame period of an image which is displayed by the display panel, and in
the waiting period, the power supply circuit is able to perform control
for reducing power supply capability, and/or the bias control circuit is
able to perform control for reducing the bias current.

20. The semiconductor device according to claim 19, wherein the power
supply circuit includes a DCDC converter that generates an internal power
source from a power source which is supplied from an outside, and a
regulator that outputs a stabilized power source from the internal power
source, the DCDC converter is able to improve power supply capability by
increasing a frequency and/or duty of a boost clock, and to reduce power
supply capability by decreasing the frequency and/or duty thereof, the
bias current is set to a first bias current, the regulator is able to
improve power supply capability by increasing a second bias current
controlled by the bias control circuit, and to reduce power supply
capability by decreasing the second bias current, and in the waiting
period, the power supply circuit is able to perform control for
decreasing the frequency and/or duty of the DCDC converter further than
that in the display driving period, and the bias control circuit is able
to perform control for reducing the second bias current and the first
bias current further than those in the display driving period.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The Present application claims priority from Japanese application
JP 2013-011071 filed on Jan. 24, 2013, the content of which is hereby
incorporated by reference into this application.

BACKGROUND

[0002] The present invention relates to a display driver and a touch
control circuit of a display panel having a touch sensor mounted thereon,
and particularly relates to a display driver and a touch control circuit
which are capable of being suitably used for a reduction in power
consumption of a circuit.

[0003] Hitherto, on-cell types in which a display panel and a touch panel
are independent of each other have been the mainstream. However, in
recent years, in-cell types capable of achieving a further reduction in
thickness in which a display panel and a touch panel are integrated with
each other have been widespread, particularly, in mobile panel modules.
Since the display panel and the touch sensor are independent of each
other in on-cell types, independent-type separate chips are also mainly
used for the display driver and the touch controller. In the separate
chips, display driving and sensing are generally performed in an
asynchronous manner. On the other hand, since the display panel and the
touch sensor share circuits in the in-cell types, display driving and
sensing cannot be performed simultaneously, and thus types in which
display driving and sensing are performed alternately in a time-division
manner have been proposed.

[0004] JP-A-2012-59265 discloses a display device in which a touch sensor
and a display element of an in-cell type are operated alternately in a
time-division manner and a method of driving the same. The sensing of the
touch sensor and the driving of the display element are performed
alternately in a time-division manner. This is a system in which one
frame is divided into a display mode and a touch sensing mode, and a gate
driver, a data driver and a touch controller are controlled by a timing
controller so that both the modes are executed alternately. In this
system, the high accuracy of touch detection is realized by
intermittently performing image display for each of several lines, and
performing touch sensing in a period in which image output from a display
driver is stopped. Since noise of a signal for driving the display
element is not mixed into a detection signal of the touch sensor, the
influence of noise can be alleviated.

SUMMARY

[0005] As a result of the examination of JP-A-2012-59265 by the inventor,
it is known that there is the following new problem.

[0006] Since a display period of an image frame is divided into a display
driving period and a sensing period, an operation is required to be
performed in each of the display driving period and the sensing period
within shorter time than in a case where an operation is performed
simultaneously and concurrently without time division. Accordingly, a
circuit operating more rapidly is required to be adopted in a display
driver and a touch sensing circuit. In order to speed up a circuit, an
element having a large element size and high current driving capability
is adopted, and thus power consumption becomes large. Further, a power
supply circuit that supplies a power source to these circuits is required
to be provided with power supply capability having a margin even at the
moment in case that power consumption becomes maximum. In addition, as a
bias current supplied to various types of circuits in a display driver
and a touch control circuit, a bias current of a current value having a
margin even at the moment in case that operation speed becomes highest is
supplied.

[0007] The present invention is contrived in view of such circumstances,
and an object thereof is to suppress an increase in power consumption in
a display driver and a touch control circuit of a display panel having an
in-cell type touch sensor mounted thereon, even in case that the display
driver and the touch control circuit are brought into operation in a
time-division manner.

[0008] The above and other problems and novel features of the present
invention will be made clearer from the description and the accompanying
drawings of this specification.

[0009] According to an embodiment, a configuration is as follows.

[0010] That is, a semiconductor device connected to a display panel
including an in-cell type touch sensor is configured as follows. The
semiconductor device includes a driving circuit capable of driving the
display panel, a touch sensing circuit which is connected to the touch
sensor, a power supply circuit that supplies a power source to the
driving circuit and the touch sensing circuit, and a bias control circuit
that controls bias currents flowing through the driving circuit and the
touch sensing circuit. The semiconductor device is able to perform a
time-division operation including a display driving period in which the
display panel is driven and a touch state is not detected and a sensing
period in which a touch state is detected and a driving state of the
display panel is not changed. One or more display driving period and one
or more sensing periods are included in one frame period of an image
which is displayed by the display panel. The touch sensing circuit is set
to be in a low power consumption state in the display driving period, and
the driving circuit is set to be in a low power consumption state in the
sensing period. For example, in the display driving period, power supply
capability to the touch sensing circuit is reduced further than that in
the sensing period, and/or the bias control circuit reduces the bias
current of the touch sensing circuit further than that in the sensing
period. In the sensing period, power supply capability to the driving
circuit is reduced further than that in the display driving period,
and/or the bias current of the driving circuit is reduced further than
that in the display driving period.

[0011] A brief description of an effect obtained by the embodiment is as
follows.

[0012] That is, even in case that a display driver and a touch control
circuit of the display panel having an in-cell type touch sensor mounted
thereon are brought into operation in a time-division manner, it is
possible to keep power consumption low.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a block diagram illustrating an outline of a
semiconductor device according to a typical embodiment.

[0014] FIG. 2 is a timing diagram illustrating an operation example the
semiconductor device according to the typical embodiment.

[0015] FIG. 3 is a block diagram illustrating a configuration of a
semiconductor device according to First Embodiment.

[0016] FIG. 4 is a timing diagram illustrating an operation example of the
semiconductor device according to First Embodiment.

[0017] FIG. 5 is an enlarged timing diagram of a portion of FIG. 4.

[0018] FIG. 6 is a block diagram illustrating a configuration of a
semiconductor device according to Second Embodiment.

[0019] FIG. 7 is a timing diagram illustrating an operation example of a
semiconductor device according to Second Embodiment.

[0020] FIG. 8 is an enlarged timing diagram of a portion of FIG. 7.

[0021] FIG. 9 is a block diagram illustrating a configuration of a
semiconductor device according to Third Embodiment.

[0022] FIG. 10 is a timing diagram illustrating an operation example of a
semiconductor device according to Third Embodiment.

[0023] FIG. 11 is an enlarged timing diagram of a portion of FIG. 10.

DETAILED DESCRIPTION

1. Summary of the Embodiments

[0024] First, the summary of typical embodiments disclosed in the present
application will be described. Reference numerals and signs in the
drawings that refer to with parentheses applied thereto in the
description of the summary of the typical embodiments are merely
illustrative of what are included in the concepts of components marked
with the reference numerals and signs.

[0025] [1]<Reduction in Power Consumption of Display Driver+Touch
Controller>

[0026] A semiconductor device (1) according to a typical embodiment
disclosed in this application is configured as follows. The semiconductor
device can be connected to a display panel (6) including a touch sensor
(7). The semiconductor device includes a driving circuit (4) capable of
driving the display panel, a touch sensing circuit (5) which is connected
to the touch sensor, a power supply circuit (2) that supplies a power
source to the driving circuit and the touch sensing circuit, an a bias
control circuit (3) that controls a first bias current flowing through
the driving circuit and a second bias current flowing through the touch
sensing circuit.

[0027] In the semiconductor device (1), a time-division operation can be
performed including a display driving period in which the display panel
is driven and a touch state is not detected and a sensing period in which
the touch state is detected and the driving state of the display panel is
not changed, and one frame period of an image displayed by the display
panel includes one or more display driving periods and one or more
sensing periods.

[0028] In the display driving period, the power supply circuit reduces
power supply capability to the touch sensing circuit further than that in
the sensing period, and/or the bias control circuit reduces the second
bias current further than that in the sensing period.

[0029] In the sensing period, the power supply circuit reduces power
supply capability to the driving circuit further than that in the display
driving period, and/or the bias control circuit reduces the first bias
current further than that in the display driving period.

[0030] Thereby, even in case that a display driver and a touch control
circuit of the display panel having an in-cell type touch sensor mounted
thereon are brought into operation in a time-division manner, it is
possible to keep power consumption low.

[0031] [2]<Boost Clock Frequency of DCDC+Bias Current of Regulator>

[0032] In paragraph 1, the power supply circuit includes a DCDC converter
(13) that generates an internal power source from a power source which is
supplied from an outside, a first regulator (15_1 and 15_2) that outputs
a first stabilized power source, supplied to the driving circuit, from
the internal power source, and a second regulator (15_3) that outputs a
second stabilized power source, supplied to the touch sensing circuit,
from the internal power source.

[0033] The DCDC converter is able to improve power supply capability by
increasing the frequency of a boost clock, and to reduce power supply
capability by decreasing the frequency thereof. The first regulator is
able to improve power supply capability by increasing a third bias
current controlled by the bias control circuit, and to reduce power
supply capability by decreasing the third bias current. The second
regulator is able to improve power supply capability by increasing a
fourth bias current controlled by the bias control circuit, and to reduce
power supply capability by decreasing the fourth bias current.

[0034] In the display driving period, the power supply circuit decreases
the frequency of the DCDC converter further than that in the display
driving period, and the bias control circuit reduces the fourth bias
current and the second bias current further than those in the sensing
period. In the sensing period, the power supply circuit decreases the
frequency of the DCDC converter further than that in the display driving
period, and the bias control circuit reduces the third bias current and
the first bias current further than those in the display driving period.

[0035] Thereby, it is possible to control the power supply capability of
the DCDC converter and the regulator constituting the power supply
circuit with high speed and efficiency, and to improve the S/N ratio of
touch sensing by reducing the generation of noise caused by the boost
clock of the DCDC converter.

[0036] [3]<Duty of Boost Clock of DCDC+Bias Current of Regulator>

[0037] In paragraph 1, the power supply circuit includes a DCDC converter
(13) that generates an internal power source from a power source which is
supplied from an outside, a first regulator (15_1 and 15_2) that outputs
a first stabilized power source, supplied to the driving circuit, from
the internal power source, and a second regulator (15_3) that outputs a
second stabilized power source, supplied to the touch sensing circuit,
from the internal power source.

[0038] The DCDC converter is able to improve power supply capability by
increasing the duty of a boost clock, and to reduce power supply
capability by decreasing the duty thereof. The first regulator is able to
improve power supply capability by increasing a third bias current
controlled by the bias control circuit, and to reduce power supply
capability by decreasing the third bias current. The second regulator is
able to improve power supply capability by increasing a fourth bias
current controlled by the bias control circuit, and to reduce power
supply capability by decreasing the fourth bias current.

[0039] In the display driving period, the power supply circuit decreases
the duty of the DCDC converter further than that in the display driving
period, and the bias control circuit reduces the fourth bias current and
the second bias current further than those in the sensing period. In the
sensing period, the power supply circuit decreases the duty of the DCDC
converter further than that in the display driving period, and the bias
control circuit reduces the third bias current and the first bias current
further than those in the display driving period.

[0040] Thereby, it is possible to control the power supply capability of
the DCDC converter and the regulator constituting the power supply
circuit with high speed and efficiency, and to improve the S/N ratio of
touch sensing by reducing the generation of noise caused by the boost
clock of the DCDC converter in the sensing period.

[0041] [4]<A Plurality of DCDC Converters and a Plurality of
Regulators>

[0042] In paragraph 1, the power supply circuit includes a first DCDC
converter (13_1) that generates a first internal power source from a
power source which is supplied from an outside, a second DCDC converter
(13_2) that generates a second internal power source from the first
internal power source, and a third DCDC converter (13_3) that generates a
third internal power source from the first internal power source. The
power supply circuit includes a first regulator (15_1) that outputs a
second stabilized power source, supplied to the driving circuit and the
touch sensing circuit, from the second internal power source, and a
second regulator (15_2) that outputs a third stabilized power source,
which is supplied to the driving circuit and is not supplied to the touch
sensing circuit, from the third internal power source.

[0043] Each of the first, second and third DCDC converters is able to
improve power supply capability by increasing the frequency and/or duty
of a boost clock, and to reduce power supply capability by decreasing the
frequency and/or duty thereof. The first regulator is able to improve
power supply capability by increasing a third bias current controlled by
the bias control circuit, and to reduce power supply capability by
decreasing the third bias current. The second regulator is able to
improve power supply capability by increasing a fourth bias current
controlled by the bias control circuit, and to reduce power supply
capability by decreasing the fourth bias current, or cut off the supply
of power.

[0044] In the sensing period, the power supply circuit reduces power
supply capability by decreasing the frequency and/or duty of the boost
clock of the first DCDC converter and the second DCDC converter and stops
an operation of the third DCDC converter, and the bias control circuit
stops the supply of power to the driving circuit from the second
regulator by decreasing the fourth bias current.

[0045] Thereby, in the semiconductor device having the driving circuit and
the touch sensing circuit integrated together, even in case that the
power supply circuit (s) is (are) included in a sharing or dispersion
manner, it is possible to appropriately control power supply capability.

[0046] [5]<Time-Division Operation for Each of a Plurality of Lines>

[0047] In any one of paragraphs 1 to 4, the display panel can display an
image frame constituted by a plurality of lines. The display driving
period is a period in which some of a plurality of lines within the image
frame are displayed, and the sensing period is set to an arbitrary period
between the display driving period and the next display driving period.

[0048] Thereby, in the display driver and the touch control circuit of the
display panel having an in-cell type touch sensor mounted thereon, even
in case that display driving and sensing are performed in a time-division
manner for each of a plurality of lines, it is possible to keep power
consumption low.

[0049] [6]<Display Driver IC>

[0050] The semiconductor device (1) according to the typical embodiment
disclosed in this application is configured as follows. The semiconductor
device can be connected to a display panel (7), and includes a driving
circuit (4) capable of driving the display panel, a power supply circuit
(2) that supplies a power source to the driving circuit, and a bias
control circuit (3) that controls a bias current flowing through the
driving circuit. A time-division operation can be performed including a
display driving period in which the display panel is driven and a waiting
period in which a driving state is not changed, and one frame period of
an image displayed by the display panel includes one or more display
driving periods and one or more waiting periods.

[0051] In the waiting period, the power supply circuit is able to perform
control for reducing power supply capability further than that in the
display driving period, and/or the bias control circuit is able to
perform control for reducing the bias current further than that in the
display driving period.

[0052] Thereby, even in case that the display driver of the display panel
having an in-cell type touch sensor mounted thereon is brought into
intermittent operation, it is possible to keep power consumption low.

[0053] [7]<Boost Clock Frequency of DCDC+Bias Current of Regulator>

[0054] In paragraph 6, the power supply circuit includes a DCDC converter
(13) that generates an internal power source from a power source which is
supplied from an outside, and a regulator (15) that outputs a stabilized
power source from the internal power source.

[0055] The DCDC converter is able to improve power supply capability by
increasing the frequency of a boost clock, and to reduce power supply
capability by decreasing the frequency thereof. Using the bias current as
a first bias current, the regulator is able to improve power supply
capability by increasing a second bias current controlled by the bias
control circuit, and to reduce power supply capability by decreasing the
second bias current.

[0056] In the waiting period, the power supply circuit decreases the
frequency of the DCDC converter further than that in the display driving
period, and the bias control circuit reduces the second bias current and
the first bias current further than those in the display driving period.

[0057] Thereby, it is possible to control the power supply capability of
the DCDC converter and the regulator constituting the power supply
circuit with high speed and efficiency.

[0058] [8]<Duty of Boost Clock of DCDC+Bias Current of Regulator>

[0059] In paragraph 6, the power supply circuit includes a DCDC converter
(13) that generates an internal power source from a power source which is
supplied from an outside, and a regulator (15) that outputs a stabilized
power source from the internal power source.

[0060] The DCDC converter is able to improve power supply capability by
increasing the duty of a boost clock, and to reduce power supply
capability by decreasing the duty thereof. Using the bias current as a
first bias current, the regulator is able to improve power supply
capability by increasing a second bias current controlled by the bias
control circuit, and to reduce power supply capability by decreasing the
second bias current.

[0061] In the waiting period, the power supply circuit can perform control
for decreasing the duty of the DCDC converter further than that in the
display driving period, and the bias control circuit can perform control
for reducing the second bias current and the first bias current further
than those in the display driving period.

[0062] Thereby, it is possible to control the power supply capability of
the DCDC converter and the regulator constituting the power supply
circuit with high speed and efficiency.

[0063] [9]<Fixation of Boost Clock of DCDC+Bias Current of
Regulator>

[0064] In paragraph 6, the power supply circuit includes a DCDC converter
(13) that generates an internal power source from a power source which is
supplied from an outside, and a regulator (15) that outputs a stabilized
power source from the internal power source.

[0065] The DCDC converter is able to improve power supply capability by
increasing the frequency or the duty of a boost clock, and to reduce
power supply capability by decreasing the frequency or the duty thereof.
Using the bias current as a first bias current, the regulator is able to
improve power supply capability by increasing a second bias current
controlled by the bias control circuit, and to reduce power supply
capability by decreasing the second bias current.

[0066] In the waiting period, the power supply circuit fixes a signal
level of the boost clock of the DCDC converter, and the bias control
circuit reduces the second bias current and the first bias current
further than those in the display driving period.

[0067] Thereby, in the waiting period, it is possible to stop the supply
of power to an unnecessary driving circuit, and to minimize a bias
current.

[0068] [10]<Combination of a Plurality of Low Power Consumption
Operations>

[0069] In paragraph 6, the power supply circuit includes a first DCDC
converter (13_1) that generates a first internal power source from a
power source which is supplied from an outside, a second DCDC converter
(13_2) that generates a second internal power source from the first
internal power source, and a regulator (15) that outputs a stabilized
power source from the second internal power source.

[0070] Each of the first and second DCDC converters is able to improve
power supply capability by increasing the frequency or the duty of a
boost clock, and to reduce power supply capability by decreasing the
frequency or the duty thereof. Using the bias current as a first bias
current, the regulator is able to improve power supply capability by
increasing a second bias current controlled by the bias control circuit,
and to reduce power supply capability by decreasing the second bias
current.

[0071] In the waiting period, the power supply circuit decreases the
frequency of the first DCDC converter further than that in the display
driving period, and/or decreases the duty further than that in the
display driving period, and fixes a signal level of the boost clock of
the second DCDC converter. The bias control circuit reduces the second
bias current and the first bias current further than those in the display
driving period.

[0072] Thereby, even in case that the power supply circuit is formed by
combining a plurality of DCDC converters and regulators, it is possible
to appropriately control power supply capability.

[0073] [11]<Time-Division Operation for Each of a Plurality of
Lines>

[0074] In any one of paragraphs 6 to 10, the display panel can display an
image frame constituted by a plurality of lines. The display driving
period is a period in which some of a plurality of lines within the image
frame are displayed, and the waiting period is set to an arbitrary period
between the display driving period and the next display driving period.

[0075] Thereby, in the display driver circuit, even in case that the
display driving circuit is brought into intermittent operation for each
of a plurality of lines, it is possible to keep power consumption low.

[0076] [12]<Touch Controller IC>

[0077] A semiconductor device (1_2) according to the typical embodiment
disclosed in this application is configured as follows. The semiconductor
device can be connected to a display panel (6) including a touch sensor
(7). The semiconductor device includes a touch sensing circuit (5)
connected to the touch sensor, a power supply circuit (2_2) that supplies
a power source to the touch sensing circuit, and a bias control circuit
(3_2) that controls a bias current flowing through the touch sensing
circuit. A time-division operation can be performed including a sensing
period in which the touch state is detected and a waiting period in which
the touch state is not detected.

[0078] One or more sensing periods and one or more waiting period are
included in one frame period of an image displayed by the display panel.
In the waiting period, the power supply circuit reduces power supply
capability, and/or the bias control circuit reduces the bias current.

[0079] Thereby, in the touch control circuit of the display panel having
an in-cell type touch sensor mounted thereon, it is possible to keep
power consumption low.

[0080] [13]<Boost Clock Control of DCDC+Bias Current of Regulator>

[0081] In paragraph 12, the power supply circuit includes a DCDC converter
(13_4 and 13_5) that generates an internal power source from a power
source which is supplied from an outside, and a regulator (15_3) that
outputs a stabilized power source from the internal power source.

[0082] The DCDC converter is able to improve power supply capability by
increasing the frequency and or the duty of a boost clock, and to reduce
power supply capability by decreasing the frequency and or the duty
thereof. Using the bias current as a first bias current, the regulator is
able to improve power supply capability by increasing a second bias
current controlled by the bias control circuit, and to reduce power
supply capability by decreasing the second bias current.

[0083] In the waiting period, the power supply circuit decreases the
frequency of the DCDC converter further than that in the display driving
period, and the bias control circuit reduces the second bias current and
the first bias current further than those in the display driving period.

[0084] Thereby, it is possible to control the power supply capability of
the DCDC converter and the regulator constituting the power supply
circuit with high speed and efficiency, and to improve the S/N ratio of
touch sensing by reducing the generation of noise caused by the boost
clock of the DCDC converter.

2. Further Detailed Description of the Embodiments

[0085] The embodiments will be described in details.

Typical Embodiment

[0086] FIG. 1 is a block diagram illustrating an outline of a
semiconductor device according to a typical embodiment.

[0087] A semiconductor device 1 according to the typical embodiment is
configured as follows. The semiconductor device includes a driving
circuit 4 capable of driving a display panel 6, a touch sensing circuit 5
connected to a touch sensor 7, a power supply circuit 2 that supplies a
power source to the driving circuit 4 and the touch sensing circuit 5,
and a bias control circuit 3 that controls a first bias current flowing
through the driving circuit 4 and a second bias current flowing through
the touch sensing circuit 5. For example, the semiconductor device can be
connected to the in-cell type display panel 6 including the touch sensor
7 integrally. The semiconductor device 1 is formed on one semiconductor
substrate such as single crystal silicon by, for example, a CMOS
integrated circuit manufacturing technique or the like, or is configured
such that these circuits are sealed in one package by a multi-chip, and
is formed as a semiconductor module.

[0088] The display panel 6 is, for example, a liquid crystal display
panel. The display panel can display an image frame constituted by a
plurality of lines, and can also display a moving image by sequentially
displaying an image of 30 frames per second. The driving circuit 4 drives
the display panel 6 by sequentially repeating an operation for applying
image data to be displayed to each pixel, for each line and for each
frame. The touch sensor 7 is formed by arranging, for example,
capacitors, and can detect a touch state and a position by detecting a
change in capacity. The touch sensor is formed integrally with the
display panel 6 in an in-cell type.

[0089] Operations of the semiconductor device 1 will be described below.

[0090] Since a touch sensor built-in display panel in which time division
is performed on a display period and a sensing period decreases the
driving capability of a display driver power supply in a sensing period
(TTouch) in which display driving is not performed within one frame
period and does not perform sensing in a display period (TDisp), a
decrease in the power supply driving capability of a touch sensor power
supply does not influence display and sensing. Therefore, it is possible
to perform a low power consumption operation without deteriorating
display and sensing performance.

[0091] In case that the averages of difference between power consumptions
by which the driving capabilities of the display driver power supply and
the touch sensor power supply are decreased are set to ΔWTouch
and ΔWDisp, respectively, the power reduction amount
ΔWpanel of the touch sensor built-in display panel is
expressed by the following expression.

ΔWPanel≈∫0T.sup.DispΔWDisp+-
∫0TTouchΔWTouch

[0092] In addition, by stopping an operation of the display driving power
supply in the sensing period or decreasing an operating frequency, a S/N
ratio can be increased by reducing operation noise of the display driving
power supply during sensing, which results in an effect of improving the
accuracy of touch detection.

[0093] FIG. 2 is a timing diagram illustrating an operation example of the
semiconductor device according to the typical embodiment. A horizontal
axis represents time, and a vertical axis schematically represents, from
above, a vertical synchronizing signal VSYNC, a display panel driving
signal, the power supply capability of the power supply circuit 2 to the
driving circuit 4 and the touch sensing circuit 5, and waveforms of a
first bias current of the driving circuit 4 and a second bias current of
the touch sensing circuit which are controlled by the bias control
circuit 3.

[0094] The semiconductor device 1 operates in a time-division manner in
which a period is divided into a display driving period in case that the
display panel 6 is driven and a sensing period in case that a touch state
and a position are detected by the touch sensor 7. One or more display
driving period and one or more sensing periods are included in one frame
period of an image displayed by the display panel 6. In the display
driving period, the display panel 6 is driven, but the detection of a
touch state is not performed. On the other hand, in the sensing period, a
touch state is detected, but the driving state of the display panel 6 is
not changed. A period from time t0 to time t6 is one frame period, a
period from time t1 to t2 and a period from time t3 to time t4 are
display driving periods, and a period from time t2 to time t3 and a
period from time t4 to time t5 are sensing periods. As long as the
sensing period is within the range of a period between the display
driving periods, the sensing period can be adjusted to an arbitrary
period.

[0095] In the display driving periods (times t1 to t2 and times t3 to t4),
the touch sensing circuit 5 is set to be in a low power consumption
state. For example, the power supply circuit 2 reduces power supply
capability to the touch sensing circuit 5 further than that in the
sensing period, and/or the bias control circuit 3 reduces the second bias
current further than that in the sensing period. Since the touch sensing
circuit 5 is not brought into operation by a time-division operation in
the display driving period, it is possible to keep the supply of power
and the bias current to the minimum necessary, and to suppress power
consumption by stopping the supply of power and the bias current insofar
as possible.

[0096] In the sensing periods (times t2 to t3 and times t4 to t5), the
driving circuit 4 is set to be in a low power consumption state. For
example, the power supply circuit 2 reduces power supply capability to
the driving circuit 4 further than that in the display driving period,
and/or the bias control circuit 3 reduces the first bias current further
than that in the display driving period. Since the driving circuit 4 is
not brought into operation by a time-division operation in the sensing
period, it is possible to keep the supply of power and the bias current
to the minimum necessary, and to suppress power consumption by stopping
the supply of power and the bias current insofar as possible.

[0097] Thereby, even in case that a display driver and a touch control
circuit of the display panel having an in-cell type touch sensor mounted
thereon are brought into operation in a time-division manner, it is
possible to keep power consumption low.

[0098] The present invention is not limited to the above-mentioned
embodiment, but it goes without saying that various changes and
modifications may be made without departing from the scope of the
invention.

[0099] For example, the display panel may be an organic electroluminescent
panel, a plasma display, and any other kinds of display panels without
being limited to a liquid crystal display panel. In addition, the touch
sensor may be any kinds of sensing types without being limited to a type
that detects a change in capacity. Further, the display panel and the
touch sensor may be an on-cell type without being limited to an in-cell
type. In addition, the power supply circuit 2, the bias control circuit
3, the driving circuit 4, and the touch sensing circuit 5 may be
integrated on a single semiconductor substrate, and may be formed to be
divided into a plurality of semiconductor chips.

First Embodiment

[0100] FIG. 3 is a block diagram illustrating a configuration of a
semiconductor device according to First Embodiment.

[0101] A semiconductor device 1 according to First Embodiment is
configured to include a display driver 1_1 and a touch controller 1_2.
The display driver 1_1 and the touch controller 1_2 are formed on one
semiconductor substrate by, for example, a CMOS integrated circuit
manufacturing technique or the like. The display driver 1_1 and the touch
controller 1_2 may be sealed in one package and be formed as a
semiconductor module. The display driver 1_1 drives a display panel 6 on
the basis of display data which is input from a host 8, and the touch
controller 1_2 discriminates between a touch state and a touch position
by sensing a touch sensor 7, and outputs touch position data to the host
8. The display panel 6 is, for example, a liquid crystal display panel.
The display panel can display an image frame constituted by a plurality
of lines, and can also display a moving image, for example, by
sequentially displaying an image 30 frames per second. The touch sensor 7
is formed by arranging, for example, capacitors, and can detect a touch
state and a position by detecting a change in capacity. The touch sensor
is formed integrally with the display panel 6 in an in-cell type.

[0102] The display driver 1_1 is configured to include a driving circuit
4, a power supply circuit 2_1 that supplies a power source to the driving
circuit 4 and the like, a bias control circuit 3_1 that controls a bias
current flowing through an analog circuit constituting the driving
circuit 4 and the like, a synchronizing circuit 9_1, a timing controller
10_1, and a power supply controller 11_1. The driving circuit 4 is
configured to includes a source amplifier 17 that outputs a source output
signal for driving a source electrode of the display panel 6, a level
shifter 18 that outputs a gate output signal for driving a gate electrode
of the display panel 6, and other amplifier 1 and amplifier 2 (16_1 and
16_2). A plurality of amplifiers can be mounted, but only two amplifiers
are exemplified. The power supply circuit 2_1 includes DCDC converters 1
to 3 (13_1 to 13_3), a DCDC control circuit 12_1 that supplies a boost
clock to these converters, and regulators 1 and 2 (15_1 and 15_2) that
stabilize internal power sources boosted and generated by the DCDC
converters 1 to 3 (13_1 to 13_3). Although not shown, a power supply
voltage stabilized by the regulators 1 and 2 (15_1 and 15_2) is supplied
to each circuit constituting the driving circuit 4. In addition, a power
source to the synchronizing circuit 9_1, the timing controller 10_1, and
the power supply controller 11_1 may be supplied from the power supply
circuit 2_1, may be supplied from another power supply circuit, and may
be supplied from the outside. The bias control circuit 3_1 is configured
to include regulators 15_1 and 15_2 of the power supply circuit 2_1, and
bias circuits 23_1 to 23_5 that determine a bias current flowing through
the source amplifier 17 and other amplifiers 16_1 and 16_2 of the driving
circuit 4. The synchronizing circuit 9_1 is an interface circuit of a
synchronous signal for synchronizing between the touch controller 1_2 and
the synchronizing circuit. Display data is input to the timing controller
10_1 from the host 8, and signals (source output signal, gate output
signal and the like) for driving the display panel 6 are output to the
source amplifier 17 and the level shifter 18 of the driving circuit 4 at
an appropriate timing. The display driver 1_1 according to First
Embodiment includes the power supply controller 11_1, and performs
control of a reduction in power consumption so as to control the power
supply circuit 2_1 and the bias control circuit 3_1 on the basis of a
timing control signal which is output from the timing controller 10_1.
Further details about the control of a reduction in power consumption
will be described later.

[0103] The touch controller 1_2 is configured to include a touch sensing
circuit 5, a power supply circuit 2_2 that supplies a power source to the
touch sensing circuit 5 and the like, a bias control circuit 3_2 that
controls a bias current flowing through an analog circuit constituting
the touch sensing circuit 5 and the like, a synchronizing circuit 9_2, a
timing controller 10_2, and a power supply controller 11_2. The touch
sensing circuit 5 is configured to include a touch detection signal
driver 19 that outputs a touch detection signal applied to a touch panel
7, a touch state detection circuit 20 that detects the touch state of the
touch panel 7, an AD (Analog to Digital) conversion circuit 21 that
converts an analog value which is output from the touch state detection
circuit 20 into a digital value, a touch position discrimination circuit
22, and other amplifiers 16_3 and 16_4. A plurality of amplifier can be
mounted, but only two amplifiers are exemplified. Touch position data
which is output from the touch position discrimination circuit 22 is once
stored in a memory 24, and then is output to the host 8. By the touch
position data being once stored in the memory 24, the host 8 can have
access to the memory 24 at an arbitrary timing, to thereby read out the
touch position data. The power supply circuit 2_2 includes DCDC
converters 4 and 5 (13_4 and 13_5), a DCDC control circuit 12_2 that
supplies a boost clock to these converters, and a regulator 15_3 that
stabilizes an internal power source boosted and generated by the DCDC
converter. Although not shown, a power supply voltage stabilized by the
regulator 15_3 is supplied to each circuit constituting the touch sensing
circuit 5. In addition, a power source to the synchronizing circuit 9_2,
the timing controller 10_2, and the power supply controller 11_2 may be
supplied from the power supply circuit 2_2, and may be supplied from the
outside. The bias control circuit 3_2 is configured to include the
regulator 15_2 of the power supply circuit 2_2, and bias circuits 23_6 to
2311 that determines a bias current flowing through the touch detection
signal driver 19, the touch state detection circuit 20, the AD conversion
circuit 21, and other amplifier 163 and 16_4 of the touch sensing circuit
5. The synchronizing circuit 9_2 is an interface circuit of a synchronous
signal for synchronizing between the display driver 1_1 and the
synchronizing circuit. The timing controller 10_2 performs timing control
of the touch detection signal driver 19, the touch state detection
circuit 20, the AD conversion circuit 21, the touch position
discrimination circuit 22, and the memory 24. The touch controller 1_2
according to First Embodiment includes the power supply controller 11_1,
and the timing controller 10_2 performs control of a reduction in power
consumption by controlling the power supply circuit 2_2 and the bias
control circuit 3_2 on the basis of a timing control signal which is
output from the timing controller 10_2, in addition to the
above-mentioned control. Further details about the control of a reduction
in power consumption will be described later.

[0104] An operation example of the semiconductor device according to First
Embodiment will be described below.

[0105] FIG. 4 is a timing diagram illustrating an operation example of the
semiconductor device according to First Embodiment, and FIG. 5 is an
enlarged timing diagram of a portion of FIG. 4 (times t10 to t15).

[0106] In the semiconductor device 1, the timing controllers 9_1 and 9_2
of the display driver 1_1 and the touch controller 1_2 are synchronized
with each other, and display driving and touch sensing are performed in a
time-division manner. The timing controller 10_1 of the display driver
1_1 performs display driving intermittently for each of several lines,
and generates display driving periods (t2 to t3, t4 to t5, t6 to t7, and
t8 to t9) and non-display driving periods (t1 to t2, t3 to t4, t5 to t6,
and t7 to t8). The touch controller 1_2 performs touch sensing in the
non-display driving periods of the display driver 1_1.

[0107] In the semiconductor device 1 of the present invention, the power
supply controller 11_1 of the display driver 1_1 further has a function
of operating the display power supply circuit 2_1 by the timing
controller 10_1 with low power consumption for a fixed period, and the
power supply controller 11_2 of the touch controller 1_2 further has a
function of operating the touch power supply circuit 2_2 by the timing
controller 10_2 with low power consumption for a fixed period.

[0108] In case that switching from the display driving period to the
non-display driving period is performed by the control of the timing
controller 10_1, the display driver 1_1 sets the display driving power
supply 2_1 to be in a low power consumption state, and transmits a
horizontal synchronizing signal DISP_HSYNC to the touch controller 1_2
through the synchronizing circuit 9_1. In case that DISP_HSYNC is
received in the synchronizing circuit 9_2, for example, at time t11, the
touch controller 1_2 releases the low power consumption state of the
touch controller power supply 2_2 at time t12 after HSYNC asynchronous
transfer time Tasync, and starts touch sensing. After the
termination of touch sensing at time t13, the touch controller power
supply 2_2 is set to be in a low power consumption state. In this case,
in case that the display driver 1_1 and the touch controller 1_2 are
formed in separate chips, a constant sensing termination margin
Tmargin may be secured until display driving is started from the
termination of touch sensing.

[0109] The touch sensor power supply 2_2 is operated with low power
consumption in the display driving period, and the display power supply
2_1 is operated with low power consumption in the non-display driving
period in case that touch sensing is performed. The low consumption
driving period can be adjusted within the ranges of the display driving
period and the non-display driving period, and the low power consumption
operation can be realized by various methods. The low power consumption
operation of the display power supply circuit 2_1 is realized by either
of the cutoff of a bias current or the reduction of the amount of a
current, the stop of the regulators 15_1 and 15_2 or the stop of the
amplifier, the stop of the DCDC converters 13_1 to 13_3, the fixation of
a switch operation to a certain state, the decrease of the frequency of a
boost clock, or the like, or by a combination thereof. The low power
consumption operation of the touch power supply circuit 2_2 is realized
by either of the cutoff of a bias current or the reduction of the amount
of a current, the stop of the regulator 15_3 or the stop of the
amplifiers 16_3 and 16_4, the stop of the DCDC converters 13_4 and 13_5,
the fixation of a switch operation to a certain state, the decrease of
the frequency of a boost clock, the stop of the touch detection signal
driver 19, the stop of the AD conversion circuit 21, or the like, or by a
combination thereof.

[0110] FIGS. 4 and 5 show an example thereof. In the display driving
periods (t2 to t3, t4 to t5, t6 to t7, and t8 to t9), on the display
driver 1_1 side, the biases of the amplifiers 15_1 and 15_2 and the
regulators 15_1 and 15_2 are set to be 100%, and the boost clock of the
DCDC converters 13_1 to 13_3 is also set to be a highest frequency. On
the other hand, on the touch controller 1_2 side, the bias of the AD
conversion circuit 21 is reduced to 10%, the bias of the touch state
detection circuit 20 is reduced to 0%, the bias of the amplifier 3 (16_3)
is reduced to 10%, the bias of the amplifier 4 (16_4) is reduced to 0%,
and the bias of the regulator 3 (15_3) is reduced to 50%, and the
frequency of the boost clock of the DCDC converters 13_4 and 13_5 is also
controlled to a frequency lower than that in the sensing period. In the
non-display driving periods (t1 to t2, t3 to t4, t5 to t6, and t7 to t8),
on the display driver 1_1 side, the bias of the amplifier 1 (15_1) is
reduced to 10%, the bias of the amplifier 2 (15_2) is reduced to 30%, and
the biases of the regulators 1 and 2 (15_1 and 15_2) are reduced to 30%
and 50%, respectively. The frequency of the boost clock of the DCDC
converter 1 (13_1) is decreased, and the level of the boost clock of the
DCDC converters 2 and 3 (13_2 and 13_3) is fixed. Thereby, a boosting
operation is stopped. In case that a capacitor connected to a power
supply is charged with charge even though the boosting operation is
stopped, more than a constant voltage is maintained. In case that it is
assured that more than a predetermined voltage is maintained in a period
until the boosting operation is resumed, the boosting operation may be
stopped. On the other hand, on the touch controller 1_2 side, the biases
of the AD conversion circuit 21, the touch state detection circuit 20,
the amplifiers 16_3 and 16_4, and the regulator 15_3 are set to be 100%,
and the frequency of the boost clock of the DCDC converters 13_4 and 13_5
is also set to be a highest frequency. A touch detection pattern is
output from the touch detection signal driver 19, and accordingly, an
analog waveform of a touch detection result is input to the touch state
detection circuit 20. The analog waveform of the touch detection result
is, for example, a waveform in which an attenuation coefficient changes
by the capacitance of a capacitor formed on the touch panel changing due
to pressure. It is possible to detect a touch state by sampling a peak
value after a predetermined time. However, the above is merely
illustrative, and the realization form of the touch sensor is arbitrary.
In the display driving period, the touch detection pattern is not output,
and it is not necessary to receive a touch detection result waveform.
Therefore, power consumption is reduced by stopping the operations of the
touch detection signal driver 19, the touch state detection circuit 20,
the AD conversion circuit 21, and the touch position discrimination
circuit 22. Specifically, a bias current flowing through the driver and
circuits is decreased, and power supply capability for the driver and
circuits is decreased. Even in case that power supply capability is
maintained just by decreasing a bias current, power consumption is
reduced by an amount corresponding to the decreased bias current. Even in
case that power supply capability is decreased in a state where the bias
current is not changed, the power consumption of the power supply circuit
is reduced. Therefore, the power consumption of the display driver 1_1 in
that period can be kept low.

[0111] The power supply capability of the DCDC converter can also be
controlled by the duty of a boost clock, in addition to the frequency of
a boost clock. In case that a capacitor is charged in a high period of a
boost clock and boosting in a low period is performed, it is possible to
decrease the amount of charge accumulated in the capacitor by shortening
the high period, and to decrease current supply capability. Here, current
supply capability and power supply capability are used synonymously with
each other, and show current values or power values of a power source
which is output from the power supply circuit such as the DCDC converter.
The relationship between the high period and the low period is determined
by a circuit configuration, and may be reversed. In an example of FIG. 5,
in the clock of the DCDC converter 1 (13_1), the magnitudes of a high
pulse are the same as each other in the display driving period and the
non-display driving period. However, a clock the duty of which is reduced
by thinning out a pulse in the non-display driving period is generated
and supplied, and thus power supply capability is reduced. Thereby, the
power consumption of the DCDC converter itself or the supply circuit of a
boost clock can be kept to the minimum necessary. It is possible to
change the power supply capability of the DCDC converter with high speed
and efficiency by changing the frequency and the duty of the boost clock
of the DCDC converter. It takes time to gradually change a clock
frequency until stabilization. However, according to thinning out or
frequency division of a pulse, the clock frequency can be changed
instantaneously without producing an unstable period. Further, it is
possible to reduce noise generated due to a boost clock. In First
Embodiment, an example is illustrated in which the display driver 1_1 and
the touch controller 1_2 are formed in separate chips. There is a concern
that the noise caused by the boost clock of the DCDC converter on the
display driver 1_1 side may be propagated to the touch controller 1_2
through power supply wiring or control wiring, and that the S/N ratio of
the touch state detection circuit 20 is deteriorated. However, since the
boost clock of the power supply circuit 2_1 of the display driver 1_1 is
suppressed to a low frequency or duty during the sensing period, the
noise to be generated is also kept low. Thereby, it is possible to
improve the S/N ratio of touch sensing in the touch controller 1_2.

[0112] A plurality of DCDC converters and a plurality of regulators are
included, and the power supply circuit is formed by a combination
thereof, thereby allowing power supply capability to be finely
controlled. For example, in an example of FIG. 4, the DCDC converter 1
(13_1) can be configured to generate an internal power source from a
power source which is supplied from the outside, and the DCDC converters
2 and 3 (13_2 and 13_3) can be configured to generate another internal
power source (for example, having positive and negative polarities at
higher pressure) from the internal power source. The DCDC converter 1
(13_1) continues an operation by decreasing the frequency of a boost
clock even in the non-display driving period, but the DCDC converters 2
and 3 (13_2 and 13_3) stop operations. The output of the DCDC converter 1
(13_1) causes the supply of power to a circuit, such as the bias control
circuit 3_1, which is not able to completely stop an operation to be
performed, and the output of the DCDC converters 2 and 3 (13_2 and 13_3)
causes the supply of power to a circuit, such as the source amplifier 17
and the level shifter 18, which stops an operation in the non-display
driving period to be performed. The boost clocks of the DCDC converters 2
and 3 (13_2 and 13_3) exemplified in FIGS. 4 and 5 are clock having
reverse phases to each other, and are suitable for a case where
positive-negative symmetric voltages, for example, are generated. The
phases of time at which mutual current consumptions become a peak are
deviated by 180 degrees due to the reversed phase, thereby allowing the
sum of peak currents of the DCDC converters 2 and 3 (13_2 and 13_3), that
is, the entire peak current to be suppressed.

[0113] The time division periods of the display driving period and the
non-display driving period or the sensing period may be specified using
the image line as a unit. Display and touch sensing may be repeated for
each line, and touch sensing may be performed after the lines of the
entirety of one frame are displayed. More preferably, the number of
appropriate lines may be obtained on the basis of the number of
electrodes of the display panel 6. By using the line as a unit, the
display driver 1_1 and the touch controller 1_2 can synchronize with each
other using a horizontal synchronizing signal DISP_HSYNC for displaying.

Second Embodiment

[0114] First Embodiment is an embodiment in which the display driver 1_1
and the touch controller 1_2 are formed in so-called separate chips. On
the other hand, Second Embodiment is an embodiment using a so-called
combo chip in which the display driver and the touch controller are
formed integrally with each other.

[0115] FIG. 6 is a block diagram illustrating a configuration of a
semiconductor device according to Second Embodiment. A combo chip 1 which
integrally includes a display driver and a touch controller is formed on
one semiconductor substrate by, for example, a CMOS integrated circuit
manufacturing technique or the like. The combo chip 1 outputs driving
signals (source output signal, gate output signal and the like) for
displaying display data which is input from a host 8 on a display panel
6, and receives a touch detection signal from a touch sensor 7. The
configurations of the display panel 6 and the touch sensor 7 are the same
as those in First Embodiment. The combo chip 1 includes a driving circuit
4, a touch sensing circuit 5, a display driver bias control circuit 3_1,
a touch controller bias control circuit 3_2, synchronous circuits 9_1 and
9_2, timing controllers 10_1 and 10_2, and a memory 24. These components
are the same as those in First Embodiment shown in FIG. 3. The combo chip
1 further includes a power supply circuit 2 and power supply controller
11_1 and 11_2. The power supply circuit 2 is configured such that the
display driver power supply circuit 2_1 and the touch controller power
supply circuit 2_2 of First Embodiment are integrated with each other,
and the circuit scale is reduced by use in common. The DCDC converter 2
(13_2) performs the supply of power to the touch sensing circuit 4 and
the like, instead of the DCDC converters 4 and 5 (13_4 and 13_5).
Thereby, it is possible to reduce two circuits of the DCDC converters.
The supply of power to the touch sensing circuit 4 and the like may be
performed from both the DCDC converters 2 and 3 (13_2 and 13_3), instead
of the DCDC converters 4 and 5 (134 and 13_5). As is the case with the
DCDC converters 2 and 3 (13_2 and 13_3), the DCDC converters 4 and 5
(13_4 and 13_5) are DCDC converters operating at a complementary boost
clock, and thus are replaced with good consistency. The power supply
controller 11_1 performs timing control of the power supply circuit 2 and
timing control of the display driver bias control circuit 3_1, and the
power supply controller 11_2 performs timing control of only the touch
controller bias control circuit 3_2.

[0116] An example is illustrated in which the synchronizing circuits 9_1
and 9_2, the timing controllers 10_1 and 10_2, the power supply
controllers 11_1 and 11_2, and the bias control circuits 3_1 and 3_2 are
provided independently from each other. Thereby, it is possible to divert
design properties which are originally mounted to the display driver and
the touch controller, to shorten a design development period, and to
suppress a design cost. On the other hand, common circuits included in
respective components can be shared and formed integrally with each
other. In this case, it is possible to reduce a circuit scale, to perform
originally asynchronous circuit operations of the display driver and the
touch controller using a synchronizing circuit, and to reduce a waste of
timing associated with the transmission and reception of an asynchronous
signal.

[0117] An operation example of the semiconductor device (combo chip 1)
according to Second Embodiment will be described below.

[0118] FIG. 7 is a timing diagram illustrating an operation example of the
semiconductor device according to Second Embodiment, and FIG. 8 is an
enlarged timing diagram of a portion of FIG. 7 (times t10 to t15).

[0119] In the semiconductor device (combo chip 1), the timing controllers
9_1 and 9_2 synchronize with each other by transmitting and receiving a
horizontal synchronizing signal DISP_HSYNC, and performs display driving
and touch sensing in a time-division manner as is the case with First
Embodiment shown in FIGS. 4 and 5. As is the case with First Embodiment
shown in FIGS. 4 and 5, a reduction in power consumption is performed on
the touch sensing circuit 5 in the display driving period, and a
reduction in power consumption is performed on the driving circuit 4 in
the sensing period. The DCDC converter 3 (13_3) supplies a power source
to only the driving circuit 4, and thus can stop an operation in the
sensing period as is the case with First Embodiment. However, the DCDC
converter 2 (13_2) supplies a power source to the driving circuit 4 and
the touch sensing circuit 5 through use in common, and thus is not able
to stop an operation even in the sensing period. However, since the power
consumption of the touch sensing circuit 5 is lower than that of the
driving circuit 4, power supply capability is reduced to conform thereto.
As shown in FIG. 8, power supply capability is reduced by decreasing the
frequency of the boost clock of the DCDC converter 2. The same is true of
the regulators 1 and 2 (15_1 and 15_2). Through use in common, the
regulators 1 and 2 (15_1 and 15_2) perform the supply of power to the
touch sensing circuit 5 and the like instead of the regulator 3, and thus
is not able to stop an operation even in the sensing period. However,
power supply capability is made to be proper by reducing a bias current
up to 70%.

[0120] In case that switching from the display driving period to the
non-display driving period is performed, the driving circuit 4 is set to
be in a low power consumption state, and a horizontal synchronizing
signal DISP_HSYNC is transmitted to the timing controller 10_2 on the
touch controller side through the synchronizing circuit 9_1. In case that
DISP_HSYNC is received, the synchronizing circuit on the touch controller
side releases the low power consumption state of the touch sensing
circuit 5 after HSYNC asynchronous transfer time Tasync, and starts
touch sensing. After the termination of touch sensing, the touch sensing
circuit 5 is set to be in a low power consumption state. In this case, in
case that the display driver side and the touch controller side are
designed asynchronously, it is necessary to secure a constant sensing
termination margin Tmargin, but a synchronous timing design is
facilitated in the combo chip 1. Therefore, there is an advantage that
Tasync and Tmargin can be made to be smaller than in a separate
chip, and more time can be allocated to touch sensing and display
driving. Further, the synchronizing circuits 9_1 and 9_2, the timing
controllers 10_1 and 10_2, the power supply controllers 11_1 and 11_2,
and the bias control circuits 3_1 and 3_2 are formed integrally with each
other, and thus can also be formed as a synchronizing circuit. In this
case, it is possible to eliminate or remarkably reduce Tasync and
Tmargin which are margins of timing associated with the transmission
and reception of an asynchronous signal.

[0121] The same method as that shown in First Embodiment can be adopted
with respect to the low power consumption operations other than the
above.

[0122] Thereby, in the display driving period, the supply of power to the
touch sensing circuit 5 in a waiting state can be kept low, and/or the
bias current of the touch sensing circuit 5 can be reduced. On the other
hand, in the sensing period, the supply of power to the driving circuit 4
in a waiting state can be kept low, and/or the bias current of the
driving circuit 4 can be reduced. Therefore, the power consumption of the
entire semiconductor device (combo chip 1) can be kept low.

Third Embodiment

[0123] First and Second Embodiments are embodiments in which the display
driver and the touch controller are brought into operation in a
time-division manner. On the other hand, Third Embodiment is an
embodiment in which the present invention is applied to the display
driver operating intermittently.

[0124] FIG. 9 is a block diagram illustrating a configuration of a
semiconductor device (display driver 1) according to Third Embodiment.
The display driver 1 is formed on one semiconductor substrate by, for
example, a CMOS integrated circuit manufacturing technique or the like.
The display driver 1 outputs a driving signal for displaying display data
which is input from a host 8 on a display panel 6. The configuration of
the display panel 6 is the same as that in First Embodiment, and a touch
sensor may be incorporated in an on-cell type or an in-cell type. The
display driver 1 includes a power supply circuit 2, a driving circuit 4,
a bias control circuit 3, a timing controller 10, and a power supply
controller 11. The power supply controller 11 has a function of operating
the power supply circuit 2 for a fixed period with low power consumption
through the control of the timing controller 10. These components are the
same as those in First Embodiment shown in FIG. 3.

[0125] An operation example of the semiconductor device (display driver 1)
according to Third Embodiment will be described below.

[0126] FIG. 10 is a timing diagram illustrating an operation example of
the semiconductor device (display driver 1) according to Third
Embodiment, and FIG. 11 is an enlarged timing diagram of a portion of
FIG. 10 (times t10 to t13).

[0127] The semiconductor device (display driver 1) performs display
driving intermittently for each of several lines, similarly to the
time-division operation of First Embodiment shown in FIGS. 4 and 5
through the control of the timing controller 10, generates display
driving periods and non-display driving periods, and performs display
driving intermittently.

[0128] In the display driving periods (t2 to t3, t4 to t5, t6 to t7, and
t8 to t9), the biases of amplifiers 15_1 and 15_2 and regulators 15_1 and
15_2 are set to be 100%, and the boost clock of DCDC converters 13_1 to
13_3 is also set to be a highest frequency. In the non-display driving
periods (t1 to t2, t3 to t4, t5 to t6, and t7 to t8), a display power
supply is driven with low power consumption. In the non-display driving
periods, the biases of the amplifiers 1 and 2 (15_1 and 15_2) are reduced
to 10% and 30%, respectively, and the biases of the regulators 1 and 2
(15_1 and 15_2) are reduced to 30% and 50%, respectively. The frequency
of the boost clock of the DCDC converter 1 (13_1) is decreased, and the
level of the boost clock of the DCDC converters 2 and 3 (13_2 and 13_3)
is fixed. Thereby, a boosting operation is stopped.

[0129] Since display driving is performed intermittently by the display
driver 1 to generate a non-display driving period, and an power supply
operation in this period is controlled, it is possible to perform a
reduction in power consumption without deteriorating display quality.

[0130] A period on which a reduction in power consumption is performed can
be adjusted within the range of the non-display driving period. In
addition, a method of a reduction in power consumption in this period can
also be adjusted. The method of a reduction in power consumption can be
realized, in addition to the above-mentioned example, by any method of
the cutoff of a bias current by the bias control circuit 3 or the
reduction of the amount of a current, the stop of the regulators 15_1 and
15_2 or the stop of the amplifiers 16_1 and 16_2, the stop of the DCDC
converter 13_1 to 13_3, the fixation of a switch operation to a certain
state, or the decrease of an operating frequency, or by a combination
thereof.

[0131] As stated above, while the present invention devised by the
inventor has been described in detail based on the embodiments, the
present invention is not limited thereto. It goes without saying that
various modifications and changes can be made without departing from the
scope of the invention.

[0132] As described previously, for example, the display panel may be an
organic electroluminescent panel, a plasma display, and any other kinds
of display panels without being limited to a liquid crystal display
panel. In addition, the touch sensor may be any kinds of sensing types
without being limited to a type that detects a change in capacity.
Further, the display panel and the touch sensor may be an on-cell type
without being limited to an in-cell type.

[0133] In addition, a period of a reduction in power consumption, a target
circuit, a method of a reduction in power consumption, and the like can
be appropriately adjusted. For example, while the temporal sensitivity of
touch sensing can be improved by making a unit of time division finer,
the control speed of a reduction in power consumption requires rapidity.